1. Field of the Invention
The present invention relates to pin-shaped parallel terminals of an electronic component, and more particularly, to pin-shaped or flat-plate-shaped parallel terminals of an electronic or piezoelectric component for being inserted in through holes formed in a printed circuit board.
2. Description of the Related Art
Conventionally, there have been provided various kinds of electronic components such as piezoelectric ceramic filters, ceramic capacitors, resistance networks, and integrated circuits. As is apparent from the appearance of these electronic components, each of the electronic components is composed of a main body of the electronic component and terminals.
FIG. 12 shows a conventional ceramic filter 1 comprising pin-shaped parallel terminals 2.
Referring to FIG. 12, in the conventional ceramic filter 1, there are formed opposing electrodes and a common electrode on both sides of a piezoelectric ceramic substrate (not shown), respectively. Thereafter, pin-shaped terminals 2 are electrically connected to these electrodes so as to be arranged substantially in parallel to each other, and the outside of the piezoelectric ceramic substrate is covered with an outer package resin 3. Further, a stop portion 4 is formed on each of the terminals 2. When the terminals 2 are inserted into through holes 6 formed in a printed board 5 and are soldered on printed electrically conductive patterns (not shown) thereof, the outer package resin 3 formed on the terminals 2 may enter the soldering boundary between each terminal 2 and the printed conductive pattern as shown in FIG. 13, and there is a possibility of causing an imperfect connection therebetween. In order to prevent any imperfect connection, the interval between the outer package resin 3 and the printed board 5 is maintained at least at a predetermined value by the stop portions 4 of the terminals 2.
When the ceramic filter 1 having the above-mentioned structure is automatically mounted in a printed board by an automatic mounting machine, the outer package resin 3 for protecting the main body 3 of the ceramic filter 1 is held by a holding unit, and then, the terminals 2 thereof are inserted into the through holes 6 formed in the printed board 5, respectively. After the terminals 2 have been inserted into the through holes 6, respectively, the upper surface of the outer package resin 3 is struck by a pressing member 7 of the automatic mounting machine as shown in FIG. 12, in order to reliably insert the terminals 2 of the ceramic filter 1 into the printed board 5 to a predetermined depth. However, the upper surface of the outer package resin 3 is often struck relatively strongly by the pressing member 7. Therefore, the outer package resin 3 may be broken by an impulsive force of the pressing member 7, or sometimes the main body itself such as the piezoelectric ceramic substrate of the ceramic filter 1 may be broken.
In order to solve the above-mentioned problems, the material of the outer package resin 3 of each of the parts, held in a tape, to be mounted by the automatic mounting machine, is replaced with another material stronger than a predetermined standard material, or as shown in FIG. 14, an outer package resin 8 made of relatively stronger resin forms a further cover on the conventional outer package resin 3. However, when a relatively strong resin is used as the additional outer package resin 8, a large stress can be caused by the hardening and constriction thereof and can act on the piezoelectric ceramic substrate. Therefore, the piezoelectric vibration is seriously influenced in such a piezoelectric device, which is very sensitive to the outside stress. In this case, deterioration of the electric characteristics thereof cannot be prevented, and also, an increase in the rate of change of the weatherproofing properties of the part can not be prevented. Furthermore, accompanying an increase in the cost of the materials and an increase in the number of manufacturing steps, the cost of the ceramic filter 1 further increases.
It is to be noted that, in FIG. 14, 70 denotes the piezoelectric ceramic substrate, 71 denotes the opposing electrode, and 72 denotes the common electrode.
In order to solve the above-mentioned problems, the present applicant proposed in Japanese utility model application No. 1-71100/1989 to form a bent portion 9, which is bent so as to be curved in the direction of the thickness of each terminal 2 or in a direction opposite to a flat surface formed by a train of the terminals 2, in a portion along the axis of each of the terminals 2, as shown in FIG. 15. The impulsive force applied in the axis direction of each terminal 2 is absorbed by a spring force of the bent portion 9 by this technique, and the main body of the electronic component can be effectively protected from the impulsive force which is applied during automatic mounting. However, in the case that the end of the bent portion 9 extends beyond the side surface of the outer package resin 3 because of a manufacturing variation of the dimension thereof, then when the electronic component 1 is held between holding fingers of the holding unit of the automatic mounting machine, a holding finger thereof may come into contact with the bent portion 9, resulting in a chucking error and causing another electronic component to be held by mistake by the holding unit.
Further, in the case that respective bent portions 9 are formed in respective terminals 2 of the electronic component 1 in the same bending direction thereof, then when the terminals 2 are inserted in the through holes 6 formed in the printed board 5, the electronic component 1 may be inclined to the surface of the printed board 5.
The invention disclosed in the above-mentioned Japanese Utility model application No. 1-71100/1989 can solve this problem, as follows. As shown in FIG. 15, the bending portions 9 are formed with alternating bending directions, such that the bending directions of each pair of adjacent bending portions 9 are opposite to each other, alternately. In this case, when the terminals 2 of the electronic component 1 are inserted in the through holes 6 formed in the printed board 5, the electronic component 1 receives a reaction spring force from both sides of a virtual surface defined by the series of the through holes 6. Accordingly, the electronic component 1 can be prevented from being inclined to the surface of the printed board 5. In case it is only desired to use two terminals of a set of three terminals 2, the center terminal 2 is cut and removed from among the three terminals 2, and then, the remaining two end terminals 2 are utilized as the terminals of the electronic component.
However, when the center terminal 2 of the electronic component 1 is cut and removed as described above, and the remaining terminals 2 are inserted in the through holes 6, the component 1 is not vertically fixed therein, since it receives a reaction spring force from one side of the above-mentioned virtual surface defined by the series of the through holes 6, since the bending directions of the respective bending portions 9 formed in both end terminals 2 are the same. This causes again the problem that the electronic component is inclined to the surface of the printed board 5 by the reaction force.